1. Technical Field
The invention is concerned with the fabrication of small circuit elements which, as generally now fabricated, entail wire winding of a soft magnetic core. An important class of elements includes transformers and inductors based on toroidal or other magnetically ungapped cores. Contemplated structures may be discrete elements or sub-assemblies, e.g. for incorporation on circuit boards. They may be constructed in situ to constitute an integral part of a circuit.
2. Description of the Prior Art
Wire wound core structures such as toroidal inductors and transformers are expensive to fabricate--generally entail turn-by-turn hand or machine winding. Relative to other circuit elements, e.g. resistors, capacitors, etc., they contribute disproportionately to the cost of completed circuitry. The problem is most pronounced for ungapped core elements in which cost is due to complex apparatus/processing associated with the turn-by-turn insertion-extraction operation of winding. Cost is aggravated by the trend toward decreasing device size.
The prevailing commercial approach continues to depend on machine or hand winding of coil turns about toroidal cores. Recognition of the problem is evidenced by proposed alternatives revealed in patent/literature study. These include: winding with multiple turns of flex circuitry, largely as constituted of parallel conductive paths (see, U.S. Pat. Nos. 4,342,976, dated Aug. 3, 1982 and 4,755,783, dated May 7, 1988; provision of parallel paths by drilling and through-plating followed by metallizing and delineating on an insulating magnetic sheet (U.S. Pat. No. 5,055,816 dated Oct. 8, 1991; as well as a variety of approaches entailing mating of boards supporting half-circuits with windings completed mechanically by use of conductive clips (see U.S. Pat. No. 4,536,733, dated Aug. 20, 1985.